KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 172 insertions, 0 deletions

diff --git a/drivers/net/ppp/pppox.c b/drivers/net/ppp/pppox.c
new file mode 100644
index 000000000..a6f72c813
--- /dev/null
+++ b/drivers/net/ppp/pppox.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/** -*- linux-c -*- ***********************************************************
+ * Linux PPP over X/Ethernet (PPPoX/PPPoE) Sockets
+ *
+ * PPPoX --- Generic PPP encapsulation socket family
+ * PPPoE --- PPP over Ethernet (RFC 2516)
+ *
+ * Version:	0.5.2
+ *
+ * Author:	Michal Ostrowski <mostrows@speakeasy.net>
+ *
+ * 051000 :	Initialization cleanup
+ *
+ * License:
+ */
+
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/compat.h>
+#include <linux/errno.h>
+#include <linux/netdevice.h>
+#include <linux/net.h>
+#include <linux/init.h>
+#include <linux/if_pppox.h>
+#include <linux/ppp_defs.h>
+#include <linux/ppp-ioctl.h>
+#include <linux/ppp_channel.h>
+#include <linux/kmod.h>
+
+#include <net/sock.h>
+
+#include <linux/uaccess.h>
+
+static const struct pppox_proto *pppox_protos[PX_MAX_PROTO + 1];
+
+int register_pppox_proto(int proto_num, const struct pppox_proto *pp)
+{
+	if (proto_num < 0 || proto_num > PX_MAX_PROTO)
+		return -EINVAL;
+	if (pppox_protos[proto_num])
+		return -EALREADY;
+	pppox_protos[proto_num] = pp;
+	return 0;
+}
+
+void unregister_pppox_proto(int proto_num)
+{
+	if (proto_num >= 0 && proto_num <= PX_MAX_PROTO)
+		pppox_protos[proto_num] = NULL;
+}
+
+void pppox_unbind_sock(struct sock *sk)
+{
+	/* Clear connection to ppp device, if attached. */
+
+	if (sk->sk_state & (PPPOX_BOUND | PPPOX_CONNECTED)) {
+		ppp_unregister_channel(&pppox_sk(sk)->chan);
+		sk->sk_state = PPPOX_DEAD;
+	}
+}
+
+EXPORT_SYMBOL(register_pppox_proto);
+EXPORT_SYMBOL(unregister_pppox_proto);
+EXPORT_SYMBOL(pppox_unbind_sock);
+
+int pppox_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	struct sock *sk = sock->sk;
+	struct pppox_sock *po = pppox_sk(sk);
+	int rc;
+
+	lock_sock(sk);
+
+	switch (cmd) {
+	case PPPIOCGCHAN: {
+		struct sk_buff *skb;
+		int index;
+
+		rc = -ENOTCONN;
+		if (!(sk->sk_state & PPPOX_CONNECTED))
+			break;
+
+		rc = -EINVAL;
+		index = ppp_channel_index(&po->chan);
+		if (put_user(index , (int __user *) arg))
+			break;
+
+		rc = 0;
+		/* PPPIOCGCHAN historically marks the userspace handoff to
+		 * generic PPP; pppd then attaches the returned channel to
+		 * /dev/ppp.
+		 */
+		sk->sk_state |= PPPOX_BOUND;
+		/* Let lockless receive paths finish queueing against the old
+		 * state.
+		 */
+		synchronize_net();
+		/* Drain packets queued before the handoff because a bound
+		 * socket is no longer readable.
+		 */
+		while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
+			skb_orphan(skb);
+			ppp_input(&po->chan, skb);
+		}
+		break;
+	}
+	default:
+		rc = pppox_protos[sk->sk_protocol]->ioctl ?
+			pppox_protos[sk->sk_protocol]->ioctl(sock, cmd, arg) : -ENOTTY;
+	}
+
+	release_sock(sk);
+	return rc;
+}
+
+EXPORT_SYMBOL(pppox_ioctl);
+
+#ifdef CONFIG_COMPAT
+int pppox_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
+{
+	return pppox_ioctl(sock, cmd, (unsigned long)compat_ptr(arg));
+}
+
+EXPORT_SYMBOL(pppox_compat_ioctl);
+#endif
+
+static int pppox_create(struct net *net, struct socket *sock, int protocol,
+			int kern)
+{
+	int rc = -EPROTOTYPE;
+
+	if (protocol < 0 || protocol > PX_MAX_PROTO)
+		goto out;
+
+	rc = -EPROTONOSUPPORT;
+	if (!pppox_protos[protocol])
+		request_module("net-pf-%d-proto-%d", PF_PPPOX, protocol);
+	if (!pppox_protos[protocol] ||
+	    !try_module_get(pppox_protos[protocol]->owner))
+		goto out;
+
+	rc = pppox_protos[protocol]->create(net, sock, kern);
+
+	module_put(pppox_protos[protocol]->owner);
+out:
+	return rc;
+}
+
+static const struct net_proto_family pppox_proto_family = {
+	.family	= PF_PPPOX,
+	.create	= pppox_create,
+	.owner	= THIS_MODULE,
+};
+
+static int __init pppox_init(void)
+{
+	return sock_register(&pppox_proto_family);
+}
+
+static void __exit pppox_exit(void)
+{
+	sock_unregister(PF_PPPOX);
+}
+
+module_init(pppox_init);
+module_exit(pppox_exit);
+
+MODULE_AUTHOR("Michal Ostrowski <mostrows@speakeasy.net>");
+MODULE_DESCRIPTION("PPP over Ethernet driver (generic socket layer)");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_NETPROTO(PF_PPPOX);